The present invention relates to open end wrenches, and more particularly to an improved structure of open end wrench which is practical for grasping and turning normal bolts and nuts of different specifications as well as worn-out bolts and nuts of different specifications.
An open end wrench is handy tool intensively used for grasping and turning bolts and nuts. A variety of open end wrenches have been disclosed having teeth, raised portions or rough grasping faces at the jaws for grasping and turning normal bolts and nuts as well as worn-out bolts and nuts. Exemplars of conventional open end wrenches are shown in Figures from 1 to 13. The open end wrench shown in FIGS. 1, 2, and 3 has two flat raised portions at the jaws. This structure of open end wrench is functional for turning normal bolts and nuts as well as slightly worn-out bolts and nuts. However, it can not positively grasp and turn excessively worn-out bolts and nuts. FIGS. 4, 5, 7, 8, 9, 10 and 11 show other different designs. These designs can grasp and turn bolts and nuts of different sizes. However, these designs can not positively grasp and turn excessively worn-out bolts and nuts. FIG. 6 shows another design of open end wrench which is similar to the open end wrench shown in FIGS. 1 to 3. FIG. 12 shows an open end wrench having rough faces at the jaws. FIG. 13 shows an open end wrench having teeth at the jaws. The open end wrenches shown in FIGS. 12 and 13 can positively grasp and turn normal bolts and nuts, however they tend to slip when turning an excessively worn-out bolt or nut.
It is one object of the present invention to provide an open end wrench which is practical for grasping and turning hexagon head bolts and hexagon nuts as well as square head bolts and square nuts. It is another object of the present invention to provide an open end wrench which is practical for grasping and turning normal bolts and nuts of different specifications as well as worn-out bolts and nuts of different specifications. According to the present invention, the open end wrench comprises a mouth defined between two jaws and nest thereof, and a longitudinal series of transversely extended flat teeth at each of the two jaws within the mouth, wherein the longitudinal series of transversely extended flat teeth includes a first tooth remote from the nest, a third tooth adjacent to the nest, and a second tooth spaced between the first tooth and the thrid tooth by a respective transverse groove; the longitudinal lengths of the first tooth, the second tooth and the third tooth are designed at a ratio of 4:3:3; the longitudinal length of the longitudinal series of transversely extended flat teeth is equal to 0.39 of the width of the mouth, and 0.77 of the distance from the front side of the first tooth to the nest. By means of the aforesaid design, the open end wrench is practical for grasping and turning normal bolts and nuts as well as worn-out bolts and nuts.